FEASIBILITY STUDIES FOR THE IMPLEMENTATION OF NUCLEAR MAGNETIC RESONANCE IN A 25T HYBRID MAGNET

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3405-3405
Author(s):  
P. J. M. VAN BENTUM ◽  
J. C. MAAN ◽  
J. W. M. VAN OS ◽  
A. P. M. KENTGENS
Keyword(s):  
Magnetic Resonance ◽  
Power Supply ◽  
Reference Signal ◽  
Low Frequency ◽  
Feasibility Studies ◽  
Feedback System ◽  
Hybrid Magnet ◽  
Simultaneous Acquisition ◽  
Field Fluctuations ◽  
Main Components

As an exploratory study for NMR experiments in the future 20 MW Nijmegen high field magnet laboratory, the possibilities of field stabilization and field gradient compensation in a 25 T hybrid magnet in the present installation were evaluated. High frequency field fluctuations from the power supply can be compensated to better than 10-3 ppm in the 10 Hz-10 kHz range using a computer controlled feedback system. Field mapping by 2H magnetic resonance using a homebuilt device not only showed that there are substantial axial but also strong radial field gradients. It can be shown that for any cylindrical multicoil Bitter magnet the main components of these gradients can be compensated with simple ferromagnetic inserts. In this way we achieved a linewidth under 5 ppm in 1 mm3 without further shimming or optimization. The low frequency drift of the field due to instabilities of the present power supply and the effects of temperature fluctuations of the coil are determined by simultaneous acquisition of an in-situ deuterium reference signal together with the signal of interest. This allows for a full compensation of the field fluctuations by deconvolution techniques. We will report preliminary NMR results on solid27 Al samples in fields up to 25 T.

scholarly journals Flyback Converter for Solid-State Lighting Applications with Partial Energy Processing

Electronics ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 60
Author(s):  
Mario Ponce-Silva ◽  
Daniel Salazar-Pérez ◽  
Oscar Miguel Rodríguez-Benítez ◽  
Luis Gerardo Vela-Valdés ◽  
Abraham Claudio-Sánchez ◽  
...  
Keyword(s):  
Solid State ◽  
Power Supply ◽  
Design Methodology ◽  
Low Frequency ◽  
Solid State Lighting ◽  
Voltage Source ◽  
Flyback Converter ◽  
Partial Energy ◽  
In Series ◽  
Energy Processing

The main contribution of this paper is to show a new AC/DC converter based on the rearrangement of the flyback converter. The proposed circuit only manages part of the energy and the rest is delivered directly from the source to the load. Therefore, with the new topology, the efficiency is increased, and the stress of the components is reduced. The rearrangement consist of the secondary of the flyback is placed in parallel with the load, and this arrangement is connected in series with the primary side and the rectified voltage source. The re-arranged flyback is only a reductive topology and with no magnetic isolation. It was studied as a power supply for LEDs. A low frequency averaged analysis (LFAA) was used to determine the behavior of the proposed circuit and an equivalent circuit much easier to analyze was obtained. To validate the theoretical analysis, a design methodology was developed for the re-arranged flyback converter. The designed circuit was implemented in a 10 W prototype. Experimental results showed that the converter has a THDi = 21.7% and a PF = 0.9686.

High-Field Nuclear Magnetic Resonance with a Newly Designed Hybrid Magnet System

2009 ◽  
Vol 48 (1) ◽  
pp. 010220 ◽  
Author(s):  
Kenjiro Hashi ◽  
Tadashi Shimizu ◽  
Teruaki Fujito ◽  
Atsushi Goto ◽  
Shinobu Ohki ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
High Field ◽  
Hybrid Magnet ◽  
Magnet System ◽  
Nuclear Magnetic

Polarization pattern of low-frequency geomagnetic field fluctuations (0.8-3.6 mHz) at high and low latitude

1999 ◽  
Vol 104 (A1) ◽  
pp. 305-310 ◽  
Author(s):  
S. Lepidi ◽  
P. Francia ◽  
U. Villante ◽  
L. J. Lanzerotti ◽  
A. Meloni
Keyword(s):  
Geomagnetic Field ◽  
Low Frequency ◽  
Polarization Pattern ◽  
Low Latitude ◽  
Field Fluctuations

Nuclear Magnetic Resonance Studies of δ-Stabilized Plutonium

2003 ◽  
Vol 802 ◽  
Author(s):  
N. J. Curro ◽  
L. Morales
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Low Frequency ◽  
Lattice Relaxation ◽  
Spin Fluctuations ◽  
Spin Lattice Relaxation ◽  
Cubic Symmetry ◽  
Magnetic Resonance Studies ◽  
Local Distortions ◽  
Nuclear Magnetic

Nuclear Magnetic Resonance studies of Ga stabilized δ-Pu reveal detailed information about the local distortions surrounding the Ga impurities as well as provides information about the local spin fluctuations experienced by the Ga nuclei. The Ga NMR spectrum is inhomogeneously broadened by a distribution of local electric field gradients (EFGs), which indicates that the Ga experiences local distortions from cubic symmetry. The Knight shift and spin lattice relaxation rate indicate that the Ga is dominantly coupled to the Fermi surface via core polarization, and is inconsistent with magnetic order or low frequency spin correlations.

scholarly journals Quiescent-Interval Single-Shot Magnetic Resonance Angiography

Diagnostics ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 84
Author(s):  
Aman Saini ◽  
Alex Wallace ◽  
Hassan Albadawi ◽  
Sailendra Naidu ◽  
Sadeer Alzubaidi ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Image Quality ◽  
Magnetic Resonance Angiography ◽  
Diagnostic Imaging ◽  
Imaging Techniques ◽  
Feasibility Studies ◽  
Subsequent Treatment ◽  
Single Shot ◽  
Contrast Enhanced ◽  
Diagnostic Imaging Techniques

Lower extremity peripheral arterial disease (PAD) is a chronic, debilitating disease with a significant global burden. A number of diagnostic imaging techniques exist, including computed tomography angiography (CTA) and contrast-enhanced magnetic resonance angiography (CEMRA), to aid in PAD diagnosis and subsequent treatment planning. Due to concerns of renal toxicity or nephrogenic systemic fibrosis (NSF) for iodinated and gadolinium-based contrasts, respectively, a number of non-enhanced MRA (NEMRA) protocols are being increasingly used in PAD diagnosis. These techniques, including time of flight and phase contrast MRA, have previously demonstrated poor image quality, long acquisition times, and/or susceptibility to artifacts when compared to existing contrast-enhanced techniques. In recent years, Quiescent-Interval Single-Shot (QISS) MRA has been developed to overcome these limitations in NEMRA methods, with promising results. Here, we review the various screening and diagnostic tests currently used for PAD. The various NEMRA protocols are discussed, followed by a comprehensive review of the literature on QISS MRA to date. A particular emphasis is placed on QISS MRA feasibility studies and studies comparing the diagnostic accuracy and image quality of QISS MRA versus other diagnostic imaging techniques in PAD.

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